Objective: To retrospectively investigate the role of contrast-enhanced ultrasonography (CEUS) in percutaneous radiofrequency ablation (RFA) in patients with liver metastases and evaluate the therapeutic efficacy of RFA assisted by CEUS. Methods: From May 2004 to September 2010, 136 patients with 219 liver metastatic lesions received CEUS examination 1 h before RFA (CEUS group), and other 126 patients with 216 lesions without CEUS examination in the earlier period were served as a historical control group. The mean tumor size was 3.2 cm and the mean tumor number was 1.6 in the CEUS group, while 3.4 cm and 1.7 in the control group, respectively (P>0.05). The clinical characteristics, recurrence results and survival outcomes were compared between two groups. Results: In the CEUS group, two isoechoic tumors were not demonstrated on unenhanced ultrasonography (US), and 63 (47%) of 134 tumors examined with CEUS were 0.3 cm larger than with unenhanced US. Furthermore, in 18.4% of 136 patients, additional 1-3 tumors were detected on CEUS. The CEUS group showed higher early tumor necrosis and lower intrahepatic recurrence than the control group. The 3-year overall survival (OS) rate and the 3-year local recurrence-free survival (LRFS) rate in the CEUS group were 50.1% and 38.3%, in contrast to 25.3% and 19.3% in the control group, respectively (P=0.002 and P<0.001). Conclusions: CEUS provides important information for RFA treatment in patients with liver metastases and better therapeutic effect could be attained. Objective: To retrospectively investigate the role of contrast-enhanced ultrasonography (CEUS) in patients with liver metastases and evaluate the therapeutic efficacy of RFA assisted by CEUS. Methods: From May 2004 to September 2010, 136 patients with 219 liver metastatic lesions received CEUS examination 1 h before RFA (CEUS group), and other 126 patients with 216 lesions without CEUS examination in the earlier period were served as a historical control group. The mean tumor size was 3.2 cm and the mean tumor number was 1.6 in the CEUS group, while 3.4 cm and 1.7 in the control group, respectively (P> 0.05). The clinical characteristics, recurrence results and survival outcomes were compared between two groups. Results: In the CEUS group, two isoechoic tumors were not demonstrated on unenhanced ultrasonography (US), and 63 (47%) of 134 examined examined with CEUS were 0.3 cm larger than with unenhanced US. Furthermore, in 18.4% of 136 patient s, additional 1-3 tumors were detected on CEUS. The CEUS group showed higher early tumor necrosis and lower intrahepatic recurrence than the control group. The 3-year overall survival (OS) rate and the 3-year local recurrence-free survival ( LRFS) rates in the CEUS group were 50.1% and 38.3%, in contrast to 25.3% and 19.3% in the control group, respectively (P = 0.002 and P <0.001). Conclusions: CEUS provides important information for RFA treatment in patients with liver metastases and better therapeutic effect could be attained.